Improvement of sinter tank steam

1. Sintering is a method of heating powdery materials (such as fine ore and concentrate) at high temperature and sintering them into blocks under the condition of incomplete melting. The proct is called sinter, and its shape is irregular and porous. The heat energy required for sintering is provided by the combustion of the carbon in the sintering material and the excess air, so it is also called oxidation sintering. Sinter mainly depends on liquid phase bonding (also known as melting sintering), solid phase bonding only plays a secondary role
modern sintering proction is a process of exhaust sintering, in which the mixture (iron ore powder, fuel, flux and return ore) is mixed with an appropriate amount of water, mixed and granulated, and then spread on the grate of belt sintering machine. After ignition, a certain negative pressure is used to exhaust air, so that the sintering process can be carried out from top to bottom. The sinter is unloaded from the sintering trolley. After crushing, cooling, granulation and screening, the finished sinter, return ore and bedding material are separated< The typical sintering proction process can be divided into eight process systems:
1) the receiving process system mainly includes mper system, receiving tank, concentrate warehouse, flux warehouse, fire extinguishing warehouse, etc., which is responsible for the receiving, transportation and storage of incoming raw materials
2) raw material preparation process system includes neutralization of iron containing raw materials, crushing of fuel, crushing and screening of flux. Its task is to prepare raw materials, flux and fuel that meet proction requirements for batching process
3) batching process system, including ore trough, disc feeder, weighing facilities, etc; According to the specified sinter chemical composition and the type of raw materials used, through calculation, each raw material is fed according to the calculated weight, so as to ensure the stability of chemical composition of mixture and sinter and the adjustment of fuel quantity
4) mixing and granulating process system mainly includes cold and hot return plate and primary mixing; Mixture ore tank, secondary mixing and other processes. Its task is to add water and wet the mixture, then mix the mixture evenly with the primary mixer, and preheat the pellets with the secondary mixer
5) sintering process system includes bedding, distribution, ignition, sintering, etc. The main task is to sinter the mixture into qualified sinter
6) the ventilation system includes bellows, st collecting pipe, st collector and fan. Chimneys, etc
7) the finished proct processing system includes hot crushing, hot screening, cooling, cold crushing, cold screening and finished proct transportation system. The task of this process is to separate 5 ~ 50mm finished sinter, 10 ~ 20mm bottom material, less than 5mm cold return ore
8) the environmental protection st removal process system is mainly to use the electrostatic precipitator system to purify the waste gas from the st points of the sintering machine tail discharge, hot screen, cooling, ore return and whole grain system. After being purified by the precipitator, the waste gas is discharged into the atmosphere. After being wetted, the st is added into the sintering mixture for sintering. Its task is to protect the environment of sintering proction
in some sintering plants in our country, the process is not perfect, some of them have no cooling, cold crushing and cold screening operations (called hot ore plants); Some of them have cooling effect, but no cold breaking, cold screening and bedding effect. In the more advanced sintering process of Baosteel, the raw material receiving, flux crushing, screening and neutralization of iron bearing raw materials are carried out in the raw material yard, and the iron bearing raw materials are mixed into a single and stable mixture by the raw material yard and directly sent to the sintering batching tank.

2. 1. The concept of sintering

a series of physicochemical changes are made on the sintering equipment after mixing and pelletizing all kinds of powdery iron containing raw materials with appropriate amount of fuel and flux and adding appropriate amount of water< At present, the belt type suction sintering machine is widely used to proce sinter. The technological process of sintering proction is shown in Fig. 2-4. It mainly includes the preparation of sintering material, proportioning and mixing, sintering and proct treatment<
process flow of exhaust sintering

> preparation of sintering raw materials

① iron containing raw materials

high iron content, particle size & lt; 5mm ore powder, iron concentrate, blast furnace st, steel sheet, steel slag, etc

it is generally required that the raw material containing iron should have high grade, stable composition and less impurities

② flux

it requires high content of effective Cao, less impurities, stable composition, about 3% water content and more than 90% particle size less than 3mm in flux

adding a certain amount of dolomite into the sinter can make the sinter contain appropriate MgO, which has a good effect on the sintering process and can improve the quality of sinter

③ the fuel

is mainly coke powder and anthracite

the requirements for fuel are high fixed carbon content, low ash content, low volatile matter, low sulfur content, stable composition, water content less than 10%, and more than 95% of the particles with particle size less than 3mm

see table 2-2 for general requirements of raw materials for sintering<

General requirements of raw materials for sintering into the plant

● proportioning and mixing

① proportioning

proportioning purpose: to obtain sinter with stable chemical composition and physical properties to meet the requirements of blast furnace smelting

commonly used batching methods: Volume batching method and mass batching method

Volumetric Batching method is based on the condition that the bulk density of materials is constant and the mass of raw materials is proportional to the volume. The accuracy is poor

the quality batching method is based on the quality of raw materials. The specific volume proct method is accurate and easy to realize automation

② mixing

mixing purpose: to make the composition of sinter uniform, the moisture content appropriate, and easy to pelletize, so as to obtain the sinter mixture with good particle size composition, so as to ensure the quality of sinter and improve the output

mixing operation: wetting with water, blending and pelletizing

according to the different properties of raw materials, one mixing or two mixing processes can be used

the purpose of one-time mixing: wetting and mixing, and preheating the material when heating the return ore

the purpose of secondary mixing is to continue mixing and pelletizing, so as to improve the permeability of sinter layer

when sintering with rich ore powder with particle size of 10-omm, because its particle size has reached the requirement of pelletizing, one-time mixing is adopted, and the mixing time is about 50s

when fine grinding concentrate powder is used for sintering, because the particle size is too fine and the permeability of material bed is poor, in order to improve the permeability, pelletizing must be made in the mixing process, so the secondary mixing is adopted, and the mixing time is generally not less than 2.5 ~ 3min<

most sintering plants in China adopt secondary mixing< Sintering operation is the central link of sintering proction, which includes feeding, ignition, sintering and other main processes

① distribution

the operation of laying the bottom material and mixture on the sintering machine trolley

when the bedding material process is adopted, a layer of small sinter with particle size of 10-25 mm and thickness of 20-25 mm is laid as bedding material before the mixture is laid. The purpose is to protect the grate, rece the st removal load, prolong the service life of the fan rotor, and rece or eliminate the slag on the grate

after the bottom material is laid, the cloth is distributed. The size and chemical composition of the mixture should be evenly distributed along the vertical and horizontal direction of the trolley, with certain looseness and smooth surface

at present, the round roller distributor is widely used

② ignition

ignition operation is to ignite the material layer surface on the trolley and make it burn

sufficient ignition temperature, suitable high temperature holding time and uniform ignition along the trolley width are required for ignition

the ignition temperature depends on the melting temperature of sintering procts. It is usually controlled at 1250 ± 50℃ < The ignition time is usually 40-60s

ignition vacuum is 4-6kpa< The ignition depth is 10-20 mm

③ sintering

accurately control the air volume, vacuum degree, material layer thickness, machine speed and sintering end point

sintering air volume: the average air volume required per ton of sinter is 3200m3, which is (70-90) m3 / (cm2. Min) according to the sintering area

Vacuum Degree: it depends on the capacity of the fan, the resistance of the exhaust system, the permeability of the material layer and the air leakage loss

material layer thickness: appropriate material layer thickness should combine high yield with high quality. The thickness of material layer is 250-500mm

machine speed: the proper machine speed should ensure that the sinter is thoroughly burned at the predetermined sintering end point. In actual proction, the speed of the machine is generally controlled at 1.5 ~ 4 m / min

judgment and control of sintering end point: control the sintering end point, that is, control the position of the trolley when the sintering process is completed. The end point of small and medium sintering machine is generally controlled at the penultimate bellows, while that of large sintering machine is controlled at the penultimate bellows

the sintering process of belt sintering machine is carried out from top to bottom. The temperature change along the height of the material layer can be generally divided into five layers, and the reaction change in each layer is shown in Fig. 2-5. After ignition, sinter layer, combustion layer, preheating layer, drying layer and over wet layer appear successively. Then the last four layers disappear one after another, and finally only the sinter layer is left< After ignition at high temperature, the fuel in the sinter gives off a lot of heat, which makes the minerals in the sinter melt. With the combustion layer moving down and cold air passing through, the molten liquid phase is cooled and recrystallized (1000-1100 ℃) to solidify into sinter with mesh structure

the main change of this layer is the solidification of the melt, accompanied by crystallization and precipitation of new minerals, the cold air inhaled is preheated, and the sinter is cooled at the same time, and the low valent oxides may be reoxidized when contacting with the air

② combustion layer

the fuel burns in this layer, and the temperature is as high as 1350 ~ 1600 ℃, which makes the minerals soften, melt and bond into lumps

in addition to the combustion reaction, the melting, rection and oxidation of solid materials and the decomposition of limestone and sulfide occur in this layer

③ preheating layer

the mixture in the lower part is preheated to the ignition temperature quickly by the high temperature exhaust gas from the combustion layer, which is generally 400 ~ 800 ℃

solid state reaction begins in this layer, crystal water and part of carbonate and sulfate decompose, and magnetite is oxidized locally< (4) the drying layer is heated by the waste gas from the preheating layer, and the temperature of the drying layer quickly rises to above 100 ℃. A large amount of free water in the mixture evaporates, and the thickness of this layer is generally 10-30mm

in fact, it is difficult to separate the drying layer from the preheating layer, which can be collectively referred to as the drying preheating layer

the pellets in this layer are heated rapidly and dried rapidly, which is easy to be damaged and worsen the permeability of the layer

⑤ over wet layer

the hot waste gas from the dry layer contains a lot of water. When the material temperature is lower than the dew point temperature of the water vapor, the water vapor in the waste gas will re condense, which makes the water in the mixture increase greatly and form over wet layer

too much water in this layer will deteriorate the permeability of the material layer and rece the sintering speed

basic chemical reactions in sintering process

① combustion reaction of solid carbon

the combustion reaction of solid carbon is as follows:
after reaction, C0 and C02 are generated, and part of resial oxygen is proced, which provides oxidation-rection gas and heat for other reactions

the composition of the exhaust gas proced by combustion depends on the sintering raw material conditions, fuel consumption, the development of rection and oxidation reactions, and the composition of the gas pumped through the combustion layer

② decomposition and mineralization of carbonates

the carbonates in sinter are CaC03, mgc03, fec03, mnc03, etc., among which CaC03 is the main one. Under sintering conditions, CaC03 begins to decompose at about 720 ℃, and chemical boiling begins at 880 ℃. The decomposition temperature of other carbonates is lower

the decomposition proct Ca0 of calcium carbonate can react with other minerals in the sinter to form new compounds, which is mineralization. The reaction formula is:

CaCO3 + SiO2 = CaSiO3 + CO2

CaCO3 + Fe2O3 = Cao · Fe2O3 + CO2

if the mineralization is not complete, there will be resial free Ca0. During storage, it will digest with the water in the atmosphere:

CaO + H2O = Ca (OH) 2

make the volume of sinter expand and pulverize<

③ decomposition, rection and oxidation of iron and manganese oxides

under sintering conditions, Fe203 can decompose when the temperature is higher than 1300 ℃

Fe304 can decompose when the sintering temperature is lower than 1300 ℃

I don't know if it can meet your needs?

3. There are two main uses of steam in sintering plant: first, the pelletizer uses steam to preheat the mixture; second, the mixture tank uses steam to preheat the mixture. The purpose is to increase the mixture temperature, rece the over wet layer and rece the fuel consumption.

4. The main technical measures to improve the sinter quality are strengthening granulation, thick bed pellet sintering, secondary fuel addition, hot air sintering, high basicity sintering, etc. at present, the main trend of sintering equipment and process development is large-scale equipment and high degree of automation. Many small and medium-sized sintering machines in China have been turned to large-scale sintering machines after blast furnace capacity expansion. The main technical measures for domestic manufacturers to improve sinter quality are to carry out thick bed operation. The key conditions for thick bed operation are the improvement of air permeability in sintering process, the matching of smoking machine capacity, and the height of sintering machine trolley fence to meet the requirements. The key to improve the air permeability of sintering process is to strengthen the granulation of sintering mixture, which is realized by reasonably controlling the particle size composition of raw and fuel, adding composite binder and appropriately prolonging the granulation time. Spraying CaCl & lt on sinter by many domestic enterprises; sub> 2</ sub> For example, rdi-3.15 of Maanshan Iron and steel group decreased from 35.05% to 23.93%. Under the same conditions, blast furnace air volume increased by 147m; sup> 3</ sup>/ 09t / (M3 ᦇ 8226; t / (M3 ᦇ 8226); d) The fuel ratio decreased by 5 kg / T Fe.

5. 15-20kwh per ton of sinter.

6. The smoke, st, waste heat and resial humidity proced in heavy metal smelting process are purified by ventilation and st removal, so that the concentration of harmful substances can meet the health standards and emission standards. Most of the raw materials for heavy metal smelting are sulfide concentrate. The main harmful substance emitted in roasting, sintering, smelting, converting and other proction processes is SO2 flue gas, whose concentration is higher than 3%, which can be used to proce sulfuric acid. The concentration of SO2 flue gas escaping from the charging port of smelting furnace, matte (matte) port, slag discharge port, Baozi room (closed chamber for conveying metallurgical melt steel container) and converter secondary hood is relatively low, and the flue gas is generally discharged into the atmosphere in a centralized or decentralized way for dilution. The basic contents of the design include: st removal in material preparation and drying workshop, ventilation and st removal in roasting and sintering workshop, ventilation and st removal in smelting workshop, ventilation and st removal in converting and refining workshop, ventilation and st removal in electrolysis workshop, etc. The material preparation and drying workshop includes concentrate warehouse, flux section, proportioning warehouse and drying section. The main st procing points of concentrate warehouse are from grab to receiving bin and from bin to belt conveyor. Generally, the st removal system is only designed at the st procing point from the silo to the belt conveyor. The inlet and outlet of flux crushing, screening and transfer points in flux section are equipped with st hood, which forms a st removal system. The upper part of the proportioning bin is provided with an exhaust and st removal system for maintaining the negative pressure of the ore bin; Each st procing point from the lower feeder to the belt conveyor is provided with a st removal cover, which forms a st removal system. The cleaning equipment of the above st removal system can select dry or wet st collectors according to the properties of st. Concentrate drying is carried out in a cylindrical drying kiln or a short drying kiln, a squirrel cage crusher and an air flow drying tube. The latter is operated in a fully closed negative pressure state, generally without a st removal system. At the end of the cylinder drying kiln, the temperature of the material is high and the moisture content is low. The ventilation, st removal, roasting and sintering belong to the pretreatment process before smelting. The fluidized bed furnace and multi chamber furnace for concentrate roasting usually adopt the methods of furnace body heat insulation and natural ventilation to eliminate the waste heat in the workshop. When calculating the natural ventilation of the workshop, the effective coefficient m of heat diffused into the working area is 0.3 for the fluidized bed furnace with heat shield, and 0.4 for the fluidized bed furnace without heat shield. The workshop of multi-storey roaster is generally a multi-storey workshop. In order to facilitate natural ventilation, the floors of each floor should be staggered in design. In the process of loading, unloading and transportation of materials before entering the fluidized bed furnace, st hood is generally set at the loading and unloading st procing points of ore bin, disc feeder and belt conveyor, and a st removal system is formed. In order to remove the st with a large amount of water vapor, a low suspended volume airtight cover is set up at the hot calcine discharging and wet ore flushing places, and the exhaust air volume is per meter. The liquid level of flushing chute is calculated as 600m3 / h. High efficiency and corrosion-resistant wet desting equipment is selected for desting system. When the materials are discharged into the dry layer of the top of the multi chamber baking furnace, although there is st emission, because it is difficult to seal the charging point on the top of the furnace, only a closed st chamber is set up there. The main harmful substances in the sintering process are st, SO2 flue gas and waste heat. The workshop should adopt comprehensive natural ventilation measures to eliminate waste heat and flue gas. The m value of natural ventilation in sintering plant is 0.33. Mechanical ventilation and st removal system is set at the head, tail and ignition furnace of sintering machine. For a 50m3 sintering machine, the exhaust air volume of its head should be 5000-7500m3 / h, that of its ignition grate should be 16000-20000m3 / h, and that of its tail should be 35000-45000m3 / h. The sintering return ore should be cooled by cylinder cooler, and the st with a large amount of water vapor will be emitted ring the cooling process. The st removal system should adopt the wet st removal equipment with high-efficiency anti-corrosion and not easy to block. Sound control 2500mm × The exhaust volume of 5000mm cylinder cooler should be 20000-30000m3 / h. According to the variety of heavy metals, concentrate composition and grade, the smelting furnace can adopt reverberatory furnace, electric furnace, closed blast furnace and flash furnace. Through the furnace wall, matte discharge and slag discharge process, a large amount of waste heat is released, accompanied by SO2 flue gas into the workshop. Usually, organized natural ventilation is used to remove waste heat and harmful gases. When smelting copper with electric furnace, m value is 0.6, and ventilation and st removal facilities are set at feeding and charging places. A rotatable smoke exhaust hood is arranged at the matte outlet, and a smoke guide and heat insulation hood is arranged on the chute to prevent radiation heat. There is a movable cover plate on the top of the baozi room, and the exhaust air volume is 18000-25000m3 / h. The slag discharge chute is provided with a lifting water jacket heat insulation cover. A closed exhaust hood is set on the water quenching slag pool, and the exhaust air volume is calculated according to the amount of slag and the amount of steam generated. Mobile fans are set in each operation post of smelting furnace. Horizontal converter is generally used for converting and refining heavy metals. The primary st content of converter is 3-15g / m3, containing S0. The concentration is 7% ～ 8%, and the treatment process is shown in the design of st collection facilities of heavy metal smelter and the design of sulphuric acid proction facilities with sulfur dioxide flue gas of heavy metal smelter. The converter is additionally provided with a rotating shroud and a secondary smoke exhaust hood on both sides of the furnace top. Taking the 100t converter as an example, the exhaust volume of the rotating shroud is 42000m3 / h, and the exhaust volume of both sides of the top is 42000m3 / h. Local air supply or mobile fan is set at the air hole behind the furnace. Copper pyrometallurgical refining is usually carried out in reverberatory furnace or rotary furnace with natural smoke hood at furnace mouth. The crude copper out of the refining furnace is cast into metal ingot or anode plate on the casting machine. A ventilation system is designed in the cooling section to discharge water vapor, and the exhaust air volume is 30000-50000m3 / h. Heavy metal electrolysis workshop belongs to high humidity workshop. The temperature of electrolyzer liquid is 35-65 ℃. The liquid surface of electrolyzer disperses water vapor and acid mist. Generally, comprehensive natural ventilation and mechanical ventilation are adopted. The ventilation volume can be calculated according to the amount of acid mist and resial humidity in different seasons, and the larger one can be determined according to the number of air changes. In the process of zinc electrolysis, H 2 and O 2 gas are separated out from the anode and cathode respectively, resulting in a large amount of acid mist. The total ventilation rate is calculated as 10-15 times / h, except that the process adds an inhibitory covering on the liquid surface of the electrolytic cell. The ventilation rate of copper and nickel electrolysis is calculated as 5 ~ 10 times / h. The ventilation rate of lead electrolysis is calculated as 3 ~ 5 times / h. When the electrolyte is purified in various tanks, the sour water gas is proced. Generally, the corrosion-resistant natural exhaust pipe is set on the tank cover, and the exhaust air volume is related to the tank size, which can be 500-1200 m3 / h. There is chlorine escaping in the purification process of nickel electrolyte. The absorption purification exhaust system should be designed according to the discharge amount of chlorine. 2% - 4% alkali solution (NaOH solution) is used as the absorption solution. Sodium hypochlorite (NaOCl) with a certain concentration of circulating absorption solution can be returned to proction for reuse or export. In the purification system of copper electrolyte, the concentration of acid mist emitted by the de copper electrolytic cell is high, and it contains a certain amount of hydrogen arsenide gas. In addition to the process that the de copper electrolytic cell is configured in a separate room, the electrolytic cell should be equipped with a movable sealing cover plate, and the exhaust system should be equipped with a water washing purification device.

8. Sintering is to mix iron containing raw materials, fuels, solvents, etc. in proportion, and then mix them into granules. After wetting with water, they are laid on the sintering equipment and ignited from top to bottom. At the same time of ignition, air is drawn from the bottom of the sintering machine. While the fuel in the mixed ore is burned from top to bottom, the fusible substances are melted and the refractory substances are wetted, The liquid phase graally cools and sticks the refractory materials together until the end of the sintering process. The obtained massive object is called sinter, also called artificial rich ore.

9. The leveler refers to the device for scraping the material surface of the platform truck. It seems to be a loosening device. There is little attention paid to the improvement. After all, it only plays the role of scraping the material surface. The leveler has a lifting mechanism, which can be lifted or lowered. Its position is determined according to the permeability of the material layer.